1. Technical Field
The present invention relates in general to a design structure, and more specifically to a design structure for tuning transistors in an integrated circuit design.
2. Description of the Related Art
The design of modern digital integrated circuits, which contain millions of transistors, is a complex task. One of the important design steps is optimization, also referred to as circuit tuning. In the tuning step, the optimal size of each transistor in the circuit is determined. Wider transistors are generally capable of handling increased electrical current, which leads to faster circuits and greater power dissipation. However, wider transistors also consume more physical area and place a heavier burden on the previous stage of logic. Determining the optimal size for each transistor yields tremendous benefits, but since an optimal size must be calculated for each individual transistor, the task can be very complex and time consuming.
Traditional optimization of electronic circuits is a manual, iterative, tedious, and error-prone task. In contrast, automated tuning, which utilizes software implementing sophisticated numerical algorithms, improves performance and increases designer productivity. Static circuit optimization implies the determination of optimal transistor and wire sizes, on a static timing basis, while simultaneously taking into account all paths through the logic. The advantages of static optimization include increased designer productivity, since an optimal circuit is automatically determined; higher quality circuits, e.g. faster, smaller, and/or lower power consumption; and the fact that all possible paths through the logic are simultaneously considered.
Current automated transistor tuning tools, such as IBM's EinsTuner™, play a key role in the circuit design process. Automated transistor tuning tools take many constraints, such as robustness, speed, timing constraints, area, input loading, and rise and fall time limits, into account to render practical tuning results. However, current automated transistor tuning tools do have limitations. Specifically, register components are not tunable by transistor-level tuning tools. This limitation is due to the inclusion of local clock buffers, also known as LCBs, inside the macro paths (i.e., schematics) and the register flip-flop and latch cells of electronic circuits. Local clock buffers are typically designed using components from standard libraries that comply with specific loading rules in order to ensure a common clock arrival and clock skew reference among all registers in the circuit. If clock arrival times are not consistent among all registers, problems (e.g., early and late timing) will arise during the operation of the circuit. Consequently, the present invention recognizes that a method and system for tuning register components and optimizing local clock buffers would be a welcome improvement.